Understanding extreme weather in an era of climate change

Scientists try to ID climate signals in weather as public draws conclusions.

The US has clearly seen some pretty extreme weather events over the last year. These events have caused both billions of dollars in property damage and endless arguments over how much can be attributed to climate change. Even as scientists work on the problem of attribution, the public has often made up its mind on what's to blame.

To try to bring some sanity to the discussion, the meeting of the American Association for the Advancement of Science hosted a session on US weather extremes. Although there were a variety of talks, three presentations nicely captured the challenges: one on the state of the US climate, another on a recent climate event, and a third on trying to convey all of this to the public.

Turning up the heat

The first speaker was Donald Wuebbles of the University of Illinois. He started out by saying that you can view the climate as a bell curve, with extreme heat and cold events occurring where it starts to flatten out to the left and right. In that view, changing the climate could do any of three things. The curve itself could shift, with hot events becoming more common and cold events becoming less frequent. You could also potentially flatten the curve, with the typical climate remaining roughly the same but the instances of extreme events increased. Or, he said, you could do both.

Depending on which aspect of the climate system you're looking at, you may get any one of these options.

For temperatures, both globally and in the US, the curve has shifted: there are far more extreme hot events than there are cold ones, a trend that has been apparent for decades. In the middle of the last century, the US was setting roughly equal numbers of hot and cold records; by the decade of the 2000s, record heat was being recorded twice as often as record cold. In 2011, the ratio was 3:1, and last year it hit a staggering 10:1, suggesting the trend shows no sign of abating.

As far as rain, the US is seeing more overall, but it's mostly falling in the Northeast and Midwest, and in the form of unusually heavy rains. The heaviest one percent of events are up everywhere, but the Northeast is seeing 74 percent more of them compared to the 1950s. The Midwest has seen a 45 percent increase, and that's been enough to make the typical one-in-twenty year event into a one-in-thirteen. The West and Southwest, meanwhile, are seeing more droughts, although the extent of this change depends on the measurement standard used to define drought.

In terms of the most dramatic weather events, hurricane intensity is going up, although the numbers have varied and the probability of their making landfall is influenced by the climate in complex ways. Huebbles said that other dramatic weather events, like tornadoes and hail storms, have a complex relationship to climate, and our understanding of this relationship is limited.

Heubbles also mentioned a variety of events that have been specifically attributed to climate change, including the recent drought in Texas, which analysts have suggested was made anywhere between two and twenty times more likely by climate change. This fact served as a great bridge to the next speaker, John Nielsen-Gammon, a Texas state climatologist.

Some areas of the country have gotten wetter, while drought is becoming more frequent in the West and South.

Dry in Texas

Nielsen-Gammon set the stage for the drought talk by noting that a few tropical storms had passed over Texas in the late summer of 2010, leaving most of the state wetter than normal. But the last storm hit on September 27, and three months later eastern parts of the state entered a drought. They were then hit by the windiest spring on record, and by June of 2011 they had run out of colors to represent the depth of the drought.

With few clouds to reflect sunlight and no water to remove heat through evaporation, the state baked, with the mean temperatures rising by 3°F. "In Texas, we call that an outlier," Nielsen-Gammon joked.

Some areas of the state went over 100 days with temperatures reaching the triple digits. All of which made the wildfires inevitable. At their peak, they covered an area that would match the size of Connecticut and Rhode Island, "and we had to throw in New York City as well." All told, the drought and fires racked up over $7.6 billion in agricultural costs.

"Saying the drought was due to climate change is like saying the airplane crashed due to gravity," Nielsen-Gammon said. It's true, but it doesn't tell you much. So, his team used climate models to try to understand the causes of the drought. One of them was La Niña, the cold phase of the tropical Pacific Ocean, which has historically been associated with reduced rainfall in Texas and neighboring states. On its own, La Niña clearly doesn't produce events like the extreme drought of 2011, so they began testing other factors.

Rather than simply stipulating La Niña conditions, the team put the actual sea surface temperatures into their model. While the event was still unusual, it was no longer an extreme outlier within the set of results produced by the models. Adding in the warming that Texas has experienced since 1995, events like 2011 "become even easier to see."

But it was still clear that La Niña was a key enabler. What does that mean for the future? As Nielsen-Gammon put it, "All the reviews agree: La Niña may get stronger, or maybe not. La Niña may get more frequent, or maybe not." In other words, we don't know how the Pacific will respond to our planet's increasing temperatures, and the ENSO cycle that swings between El Niño and La Niña is complex and variable, making the identification of long-term trends very challenging. Right now, we simply don't have enough data to know.

Managing complexity

If Nielsen-Gammon's job was complicated by the mix of natural variation and climate-driven events, then Andrew Freedman has an even greater challenge: accurately conveying it to the public. He's on the staff of Climate Central, an organization that is funded by everyone from the Nature Conservancy to the Army Corps of Engineers, and he is tasked with getting accurate climate information out through a variety of outlets.

Freedman said that the public can no longer escape paying attention to climate change, because the distinction we used to make between weather and climate change has vanished. In the last year alone, lots of events—the sea ice record, the warmest year in the lower 48, the warmest La Niña year on record, Australia's need for a new color to register the record heat on its temperature maps—all made the news, often as part of the weather reporting.

Even if scientists and reporters are cautious about how they describe the events, people are not. People have a fundamental drive to try to understand the world around them (Freedman quoted climatologist Gavin Schmidt as saying, "people are actively trying to interpret their world"), and in Freedman's words, "people are connecting dots ahead of media and scientists." In some cases, that means they'll see patterns that don't actually exist.

For example, the warming climate has driven sea level rises that will ensure that normal events have more significant consequences, as New York City experienced with Sandy. But on the other side of the globe, the Thai floods that set back the hard drive industry were largely caused by poor water management upstream. And Freedman noted the big blizzard that had just hit Boston the week before the meeting was a classic northeaster, which is not an exceptional event.

To try to get accurate information to the public, Climate Central is working with TV meteorologists, who already reach the public but don't always have the tools to handle the complexities well. And the emphasis is on getting them to ask better questions—instead of "did global warming cause this?", they should focus on questions that are more relevant and can be answered, like "how did it [climate change] influence the odds for or severity of this event?"

This certainly won't guarantee that we'll end up with a public that can easily grasp the complexities of climate. But it could help them to start recognizing that the complexities exist.

170 Reader Comments

We have to be prepared because extreme weather in an era of climate change is far more extreme than extreme weather that was merely extreme, and not extremely extreme, ever was in eras of climate stability.

At least this research ought to help provide a rebuttal to all the people who seem to think that climate change will just mean the thermostat going up, making colder places more temperate, and providing them with new economic opportunities. Yes, Canada will have more land thawing out. Meanwhile the entire Eastern Seaboard will get scrubbed off the planet. I'm sure that balances out.

Isn't the climate *always* changing? It pretty much goes through cycles of warming and cooling between ice ages, so its never actually static?

I think the real thing that gets scientists worried about this phase of climate change is that it's happening at a rate without precedent in the geologic record.

NatGeo had an issue a number of years back about climate change, and the only thing I remember from it was this note (paraphrasing)... Since 1900 the average global temperature has risen ~1C, an increase in 100 years that under normal climactic variation you usually see at the scale of thousands of years.

Just a word to the wise: Ars has a large contingent of what appear to be paid climate skeptics, so use your filters carefully. Among scientists, there is just about zero controversy that this is happening. We're just grappling with how fast it's happening, not if it's true or not.

The controversy is manufactured by powerful entities that don't want things to change, that don't want their business models, those of externalizing costs on others, to change. And there appears to be a large astroturf climate contingent that has been hitting Ars hard, in nearly all of these articles.

There is no real controversy here, just a struggle to understand the scope of a problem. Anyone that says otherwise is most likely being paid by the industries causing the problem.

Isn't the climate *always* changing? It pretty much goes through cycles of warming and cooling between ice ages, so its never actually static?

I think the real thing that gets scientists worried about this phase of climate change is that it's happening at a rate without precedent in the geologic record.

NatGeo had an issue a number of years back about climate change, and the only thing I remember from it was this note (paraphrasing)... Since 1900 the average global temperature has risen ~1C, an increase in 100 years that under normal climactic variation you usually see at the scale of thousands of years.

Based on ice core records that have shown spikes in CO2 in the near geological past ~120k year ago, I did a simple calculation that demonstrated the current rate of change in CO2 emission is very close to 100x greater than the prehistoric cyclical increases.

The bell curve moves and narrows. When discussing climate, it is not just shift, grow, or shift and grow, it can also be shift and narrow.

For instance, if the jet stream moves, or increased desertification can lead to a narrowing of the weather bell curve, as weather becomes more consistent and hotter. True, many places aren't experiencing it, but it is happening in some places.

Isn't the climate *always* changing? It pretty much goes through cycles of warming and cooling between ice ages, so its never actually static?

The fact that so many people don't seem to know this, to me, is an indication of how crappy our science classes have become in public schools. I remember being taught this as a kid back in the 70's and 80's. It's irrefutable yet people try to tell us the climate is only changing because of us humans. It’d be hilarious if it weren’t so pathetic.

Isn't the climate *always* changing? It pretty much goes through cycles of warming and cooling between ice ages, so its never actually static?

You are not a stranger to these threads. You know the drill by now. Climate has been pretty dang stable over the last 10,000 years, a time during which humans had the chance to develop little niceties like agriculture and civilization.

g0m3r619 wrote:

Just like how the climate is always in a state of change there has always been "extreme" weather. Leave it to a short lived intelligent species like ours to actually think the climate doesn't change.

Leave it to Gomer to build up a total straw man and attribute it to the people he disagrees with. In reality, warming trends drive increased extremes for certain metrics (like heat waves). What we would expect to happen in a stable climate with no overarching trend is for record temperature events and other temperature-related extremes to become less frequent over time. This is because each new record has to be more extreme than the previous record, and without a trend driving them the extremes have little physical ability to outstrip themselves going forward. It would therefore take longer and longer amounts of time for the convergence of conditions necessary to create new extreme records. What we seen in the actual data is that the warming trend is driving extremes up to record levels far more frequently than they should be, especially extreme temperature events. Extreme heat is also outpacing extreme cold, which only makes sense given the direction of the trend. Extremes happen on top of the underlying climate. If the climate isn't moving, the extremes need more work put into them to break records, so it's less likely that they will. If the climate is warming, then the conditions that might have resulted in only a non-record event before can more easily and readily break old records. This is what's happening in the world outside your window, no matter how denialists try to spin it. As for your denialist spin source, consider that not all extremes are expected to go up in a warming world. Consider also that central Europe is not the world. Consider also finding other, more reliable and accurate sources of information. Consider not posting here until you have an inkling of what the fuck you're talking about, because every climate thread you enter turns into a slog. I hope everyone will take the opportunity to downvote or ignore you here, so that your vacuous objections will disappear into the ether instead of drawing more fire. It's what I'm going to be doing from this point on.

Very nearly the only summary of climate change I have heard consistently is:"The climate is changing. It would actually be surprising if it was completely stable. Some of the changes we are currently seeing are not necessarily good for humanity. It is not clear exactly how much human activity plays into these unfavorable changes, but it probably isn't helping."

Personally, I'm not going to rush out and "go green". But I'm also not going to blithely dismiss that we may have some kind of impact, in either direction (eventually).

Isn't the climate *always* changing? It pretty much goes through cycles of warming and cooling between ice ages, so its never actually static?

I think the real thing that gets scientists worried about this phase of climate change is that it's happening at a rate without precedent in the geologic record.

NatGeo had an issue a number of years back about climate change, and the only thing I remember from it was this note (paraphrasing)... Since 1900 the average global temperature has risen ~1C, an increase in 100 years that under normal climactic variation you usually see at the scale of thousands of years.

Based on ice core records that have shown spikes in CO2 in the near geological past ~120k year ago, I did a simple calculation that demonstrated the current rate of change in CO2 emission is very close to 100x greater than the prehistoric cyclical increases.

Actually the atmosphere was MUCH thinker in those times than it is today. Scientific and verifiable fact.

Freedman said that the public can no longer escape paying attention to climate change, because the distinction we used to make between weather and climate change has vanished.

2010 - Colder than usual "Weather is not climate change!"

2011 - Hotter than usual "Of course there is climate change! Look at the weather!"

And this is why people STILL don't believe in climate change. Get the message straight, be consistent, and people will be much more likely to listen. That's the bottom line, right?

Still, this is a good start. It acknowledges that there is still a lot we don't know, which is actually one of the more convincing things about it. Generally in science, the more certain someone is of a doom-and-gloom prediction (or a bright-new-future one, for that matter), the kookier they are. Admitting that there are things we don't know, and specifying where our knowledge ends is a huge leap in credibility compared to the usual climate-chage fare.

I agree. Too many politicians and bureaucrats jumped in on the climate change bandwagon early on - the idea has become so politicized that some of its non-scientist proponents border on near religious devotion to the idea that humans have perfect understanding of the changing climate. A fellow student in one of my classes a couple of semesters back shouted down one of my professors when he dared to (off-handily) criticize some reconstructions of climate based on tree rings. (What a heretic!) Never mind that that is a controversial area of the science, this poli-sci-major-with-a-certificate-in-environmentalism knows best.

In general, I place great faith in the scientific method and the scientific process. Science does not best operate by people yelling insults and criticisms at each other. Instead, we need the people making reasoned arguments on the subject to argue out the merits of different models and approaches. Not some politician and not some crack reading conspiracy theory sites in his mom's basement.

Actually the atmosphere was MUCH thicker in those times than it is today. Scientific and verifiable fact.

Given that it actually wasn't thicker 120K years ago, i'd be very curious as to where you received the verification of this fact from. Linkage?

Talking further back. Pointing out the fact that even the make up of our atmosphere changes drastically. It you want to talk about the effects of CO2 then explain to me this. If CO2 levels drive climate change and warming of the planet then why is it land the Vikings used to farm is now locked in ice? CO2 levels are HIGHER today than they were back then.

Why would you talk 'further back' when the original comparison was CO2 rates of change from ~120k back to maybe 800k ago or so?

100x faster, this is unprecedented during any time of homo sapiens existence no matter what your Viking farmers have to say.

Just a word to the wise: Ars has a large contingent of what appear to be paid climate skeptics, so use your filters carefully. Among scientists, there is just about zero controversy that this is happening. We're just grappling with how fast it's happening, not if it's true or not.

The controversy is manufactured by powerful entities that don't want things to change, that don't want their business models, those of externalizing costs on others, to change. And there appears to be a large astroturf climate contingent that has been hitting Ars hard, in nearly all of these articles.

There is no real controversy here, just a struggle to understand the scope of a problem. Anyone that says otherwise is most likely being paid by the industries causing the problem.

I often express skeptical viewpoints on climate stories here on Ars. I am not a "paid climate skeptic". I am not beholden to any powerful entity. I don't follow Fox News and I don't believe in Intelligent Design.

There are skeptical voices on Ars that are very much genuine, honest, and based on a personal evaluation of the scientific evidence. I am one of them.

Actually the atmosphere was MUCH thicker in those times than it is today. Scientific and verifiable fact.

Given that it actually wasn't thicker 120K years ago, i'd be very curious as to where you received the verification of this fact from. Linkage?

Talking further back. Pointing out the fact that even the make up of our atmosphere changes drastically. It you want to talk about the effects of CO2 then explain to me this. If CO2 levels drive climate change and warming of the planet then why is it land the Vikings used to farm is now locked in ice? CO2 levels are HIGHER today than they were back then.

In other words, your statement was false.

I know the term "strawman" gets thrown around loosely in forums, but your posts define it.

"People think climate never changed before!!!11!" My brain implodes.

"People think that CO2 is the only factor in the climate system!!!!!11!1!" My brain explodes.

"If CO2 isn't the only factor, then it can't be significantly affecting climate today!1!" My brain runs into that little drain in the corner.

Please stop the brain violence.

It would be easy for me to tell you that LeBron James is a terrible basketball player if I thought LeBron James was a small, gray mouse. Facing the mighty man himself, I would have to admit that I just don't like him very much, and please, please don't hurt me.

Of course the climate has always changed. And the world has continued.Of course species have gone extinct and new ones have evolved to take advantage of the available niches.

Why should we be concerned about this particular piece of climate change?

Because this time a large civilisation and population is present.

Why are our cities where they are? Because of climate and geography.Why are our farms where they are? Because of climate and geography.Why are out populations where they are? Because of climate and geography.

I don't particularly care about the Earth, it's going to keep spinning. I'm only slightly concerned about species, in the long term all species go extinct and are replaced. No, I'm concerned about us.

All the evidence is saying that the climate is changing at a rate unprecedented in the history of human civilisation; and if the climate changes, then this is going to have massive potential risks on where our farms, cities and populations live across the globe. America is one of the global bread baskets. If you go into long term drought, food costs will rise across the globe.

Isn't the climate *always* changing? It pretty much goes through cycles of warming and cooling between ice ages, so its never actually static?

The fact that so many people don't seem to know this, to me, is an indication of how crappy our science classes have become in public schools. I remember being taught this as a kid back in the 70's and 80's. It's irrefutable yet people try to tell us the climate is only changing because of us humans. It’d be hilarious if it weren’t so pathetic.

..aaand another straw man battler steps forward.

Nope. You people claim we need to stop "climate change." If you don’t mean climate change then fucking say what you mean and stop being so deceptive in your wording.

Anthropogenic climate change. That is very clearly laid out and explained, with a good deal of effort gone into separating out background climate variation from that initiated by human impact. Do not lay the blame on others for your choice to misinterpret, or inability to read.

P.S. Given that this has been directly explained to you repeated, it seems a whole lot more likely it your choice…or you have one hellva cognitive deficiency.

"Unprecedented" - You keep using this word, but I don't think it means what you think it means.

Not that I don't believe in efficiency, responsibility, and conservation of resources - I've been harping about those to everyone around me since aerosols, CFC's, & the ozone layer in the mid 80's - but, there is definitely precedent for rapid climate change taking place in the Earth's past.

If you're replying to my post, please point out when, in homo sapiens' existence, the rate of change in climate was anywhere close to that being driven by the current CO2 release.

I'm fully aware that asteroid impacts caused fairly dramatic shifts in climate. But I doubt you want to use that connection if you're trying to defuse climate alarmism.

Nothing but junk science. Show me weather data from current back one billion years. Then we can have a discussion. What will the data look like? Periods of higher and lower temperatures. Period. Some years are hotter. Some colder. The world has not ended.

Tell that to the mastodons. Do you ever wonder WHY temperatures go up and down, or are you just satisfied that they do and that it will never be a problem for the things living on this planet at the time?

Nothing but junk science. Show me weather data from current back one billion years. Then we can have a discussion. What will the data look like? Periods of higher and lower temperatures. Period. Some years are hotter. Some colder. The world has not ended.

Nobody is saying the world will end. However, it might have significant consequences for the human race, if thats too much junk science for you maybe you need to limit yourself to the sports pages?

Just a word to the wise: Ars has a large contingent of what appear to be paid climate skeptics, so use your filters carefully. Among scientists, there is just about zero controversy that this is happening. We're just grappling with how fast it's happening, not if it's true or not.

The controversy is manufactured by powerful entities that don't want things to change, that don't want their business models, those of externalizing costs on others, to change. And there appears to be a large astroturf climate contingent that has been hitting Ars hard, in nearly all of these articles.

There is no real controversy here, just a struggle to understand the scope of a problem. Anyone that says otherwise is most likely being paid by the industries causing the problem.

I often express skeptical viewpoints on climate stories here on Ars. I am not a "paid climate skeptic". I am not beholden to any powerful entity. I don't follow Fox News and I don't believe in Intelligent Design.

There are skeptical voices on Ars that are very much genuine, honest, and based on a personal evaluation of the scientific evidence. I am one of them.

Given your claimed skepticism, can you detail your concerns with the theory as it stands and what it would take to address those concerns? When they are addressed, will you then accept that and change your point of view, or will you simply shift the goalposts?

Skepticism is a very specific thing. It is a willingness to become convinced and change ones mind. To be a true skeptic, one must have specific things they are skeptical about, and be willing to accept information that addresses those concerns.